The instant invention relates to a process to piece to a spinning device following yarn breakage, using a pneumatic torsion device with an injection component which is separated from a torsion component by a gap open to the atmosphere, in which the yarn is threaded into the pneumatic torsion device from the outlet side, with the help of negative pressure, and to a device to carry out said process.
According to a known process, the yarn is sucked from the side opposite to the draw-off rolls through the torsion nozzle brought into threading position (see German published application No. 3,411,577 corresponding with U.S. Pat. Nos. 4,550,560 and 3,413,894 corresponding with U.S. Pat. No. 4,545,193). In this case for spinning only a single nozzle is used which not in every case leads to acceptable results with respect to the spun yarn.
For the production of bulky yarn it is also already known to provide an injector nozzle in front of the torsion nozzle, those two nozzles being arranged one relative to the other in such a manner that a gap exists between them (See German published application No. 3,237,990). Since air enters through this gap, strong negative pressure is required in the two nozzles for the threading of the yarn.
It is therefore the object of the instant invention to create a process and a device which make it possible to thread the yarn into the nozzles, separated from each other by an air gap, in a simple manner and with low air consumption.
This object is achieved according to the invention in that the gap is sealed against the atmosphere before threading of the yarn, the yarn is then threaded into the torsion element in opposite direction to the draw-off direction and the gap is laid open again, at the latest at the beginning of draw-off of the pieced yarn. By sealingly closing the gap before threading, the negative pressure applied to the mouth which constitutes the inlet side during normal spinning of the torsion element can exert its full force at the mouth of the torsion element which constitutes the outlet side during normal spinning. The intensity is thus unaffected by extraneous air penetrating through the gap. With the gap being covered, the yarn is again threaded into the torsion element and is combined with the fiber sliver or roving being fed to the machine. The gap is laid open before or during piecing, at the latest when draw-off of the pieced yarn begins, so that the withdrawal of the yarn is not affected.
In a simple embodiment of the process of the invention, sealing of the gap can be effected by covering it. In this case it is possible to utilize the movement of the torsion element from its spinning position into a threading position and to seal the gap through the transfer of the torsion element into its threading position. However, an axial movement of the injector nozzle and/or of the torsion nozzle can also be produced for this purpose, so that the gap is closed by the relative axial movement of injector nozzle and torsion nozzle.
To carry out the described process the invention provides for the utilization of a sealing device which can be associated to the gap between injector nozzle and torsion nozzle during the threading phase, so as to prevent penetration of extraneous air into the interior of the torsion nozzle.
The sealing device is advantageously formed as a screen which can be associated to the gap. In an advantageous embodiment of this device according to invention, the torsion element is provided with an elastic element by means of which it is held against a stop determining the spinning position, while the screen associated to the gap is also used as a driving device by means of which the torsion element can be brought into the threading position. The torsion element can be supported pivotably and can be applied sealingly against the screen through swivelling around its swivelling axle.
The screen can take various forms and can be associated to the gap in different ways. For example, a stationary screen can be provided, whereby the gap can be associated to it for sealing closure through the movement of the torsion element from its spinning position into its threading position.
Sealing of the gap is also possible if the torsion nozzle and the injector nozzle can be brought into contact with each other through axial shifting of at least one of these two nozzles so that the gap between the two nozzles is closed.
Another advantageous embodiment of the object of the invention provides for the torsion nozzle and/or the injector nozzle to be equipped with a sleeve-like screen which can be brought by axial shifting into a position covering the gap between torsion element and injector nozzle.
In an especially simplified and advantageous embodiment of the device according to invention, the suction pipe can be pressed against the inlet side of the torsion element in such a manner that the gap between the injector nozzle and the torsion nozzle is closed. Depending upon the design of the object of the invention, the suction pipe either presses the elastically supported injector nozzle against the torsion nozzle or pushes the sleeve-like, also elastically supported screen to a point beyond the gap between injector nozzle and torsion nozzle.
By means of the process of the invention and of the device made in accordance with the invention, threading of the yarn into the torsion element can be carried out in a simple manner with the help of relatively little negative pressure and therefore economically. Since the aspiration of extraneous air through the gap between injector nozzle and torsion nozzle is eliminated, the threading negative pressure is exerted with full intensity upon the outlet side (during normal spinning) of the torsion element.